Cellulosic articles



CEILULOSIC ARTICLES Thomas F. Banigan, Kenmore, N. Y., assignor, by

' mesne'assignments, to E. I. du Pont de Nemours 8: Company, Wilmington, Del, a corporation of Delaware No Drawing. Application Aprill, 1936.

Serial No. 72,150

4 Cl. (Cl. 18-48) This invention relates to the manufacture of porous and more particularly, it relates to methods and apparatus for the production of porous, cellulosic masses such as, for example, artificial sponges. The invention will be described with particular reference to the manufacture of sponges from viscose. However, the invention in its broad aspects is applicable to the puction of all types of flexible, porous masses from solutions or dispersions of substances or compositions which remain alkaline or non-acid in reaction during coagulation, and particularly lated'm was removed from the molds and washed and purified. The sponge mass was then dried and cut up into sponge blocks oi the desired i coagulation of these viscose sponge masses been carried out by one of several methods. One of the most efiective of these methods is by means of a boiling salt solution, as disclosed in U. 8. Patent No. 1,909,629. When this method is employed, the iron molds within which the sponge a are pressed are placed in a bath containing the ebullient, coagulating liquid. In the interests oi economy, the vat itself and most of the equipment contacting the liquid are customarily made of iron or steel. It has been found, however, that when iron or steel-equipment is used, the sponge masses are, contaminated by and contain precipitated therein considerable quantities of iron sulfide which weaken the sponges and detract from their appearance. It has been suggested, in order to overcome this difilculty, to construct the molds and other equipment out of non-corrodible materials, such as nickel, stainless steel, etc., but the cost of doing so is almost prohibitive.

It is therefore an object of this invention to accomplish the coagulation of artificial sponges, or other porous material from viscose or the like, without the unsightly deposition of iron sulfide and other iron compounds therein.

Another object of this invention is to accomplish this result while still using the ordinary iron or steel equipment and coagulating with a hot or boiling solution of non-acid character.

Other objects or the invention will appear hereinafter.

The objects of this invention are accomplished Q in general by adding to the coagulating bath above described a small quantity of trisodium phosphate or other alkali metal phosphate.

In accordance with the invention a sponge mass is prepared from viscose as is well known 1m in the prior art. This will contain in addition to the viscose, a pore-forming material, such as sodium sulfate decahydrate, and preferably a strength giving material, such as vegetable fibers. The mass is then molded under pressure and it placed in a hot or boiling, non-acid, coagulating and regenerating solution, such as a boiling salt solution, for a suitable period, e. g. several hours, during which time the viscose is completely coagulated and regenerated. This coagulating and m regenerating solution contains, in addition to the coagulant and regenerant for the viscose, such as sodium sulfate, 9. small quantity of trisodium phosphate, or other alkali metal phosphates, e. g. the potassium salts, in quantity between 0.02% w and 1.00%, based on the weight of the coagulating bath liquid. Other phosphates, for example the mono and diphosphatcs, may be used. After this action, the sponge masses are removed, washed, purified and dried as desired. W

The following example illustrates a preferred mode of operating in accordance with this invention. V

A pressed and molded sponge mass is introduced into an iron container and the latter 35 placed in an iron vat containing a boiling solution containing about 12% sodium sulfate and 0.10% to 0.20% of trisodium phosphate. The boiling continues for 11.5 hours at a temperatu're of about 100101 C.

Sponges produced in accordance with this invention have been observed to be clean, containing no objectionable deposits of iron sulfide which might impair the appearance and strength of the sponge mass.

Although the invention has been described particularly with respect to the manufacture of artificial sponges, the invention broadly comprehends the manufacture of various other types of products, e. g. film, ribbons, threads, etc., where so the coagulating bath is non-acid and the coagulation takes place in the presence of substantial amounts of iron, e. g. in iron or steel lined tanks.

Although the invention exhibits its greatest utility when the alkali-metal phosphate is diasolved in the coagulating bath, the broadest scope of the invention includes the introduction of the alkali-metal phosphate into the viscose prior to molding and coagulation although this latter procedure is not preferred. This procedure is of additional advantage where the coagulation is not attested by means of a liquid coagulating bath. a For example, where a molded viscose mass containing pore-forming material, e. g. sodium sulfate decahydrate. is coagulated in an iron mold by a non-liquid heating agent such as steam or other source of heat which does not involve the use of a liquid coagulant, the presence of an alkali-metal phosphate diminishes or eliminates staining which might arise from the formation or iron sulfide.

As the invention is capable ot'being modified 1 within wide limits, any embodiment which conforms to the spirit of the invention is intended to be included within the scope of the claims.

I claim:

1. The process of making porous objects from molded masses containing viscose and a poreiorming material, which comprises molding the mass in a container comprising ferrous metal in contact with said mass andcoagulating the mass while still contained in the container, by subjecting the mass to the action 01' a non-acid coagulating liquid containing a small amount of a non-acid alkali metal phosphate. a

2. The process 01' claim 1 characterized in tha the phosphate is a non-acid sodium phosphate.

3. The process of claim 1 characterised in that the coagulating liquid is a hot salt solution containing a small amount of a non-acid alkali metal phosphate.

4. The process of claim 1 characterized in that the coagulating liquid is a hot salt solution containing a small amount of tri-sodium phosphate.

THOMAS l". BANIGAN. 

